Structural characterization of Ti implanted AlN
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J.P. Dallas CECM, 15, rue G. Urbain, 94407 Vitry Cedex, France (Received 20 October 1994; accepted 17 August 1995)
Sintered A1N ceramics were implanted by 1 X 1017 Ti/cm 2 at an energy of 70 keV in order to investigate the role of the chemical properties of the implanted species on the phase formed during the implantation process. The implanted ions were found in a depth profile corresponding to the calculated distribution of the vacancies produced during the implantation process instead of the predicted ion profile. Identification of the local environment of Ti and of the resulting phase led us to conclude that Ti is surrounded by N after the collision cascade and forms TiN after post-implantation annealing. The TiN nucleus if formed by substitution of Al by Ti. Therefore, the heat of formation, which is more negative for TiN than for A1N, is found to be a key parameter to predict the final system.
I. INTRODUCTION The high thermal conductivity, in addition to a thermal expansion coefficient close to that of silicon,1-2 makes A1N a promising candidate as a support in very large scale integrated (VLSI) technology. The metallization of the ceramic surfaces is one of the most important questions for this application. A technique to modify the surface is ion implantation, where nearly any kind of ion can be introduced in the matrix, even those immiscible in thermodynamical equilibrium. Solubility limits can usually be overcome. Thus, ion implantation seems to be a good tool to better understand the chemical metalceramic interaction. In the collision cascade initiated by the implanted ion, the system is in a quasi-liquid state for 10~" —10~10 s,3 during which chemical bonds are broken. The question is how the atoms will rearrange after the cascade. As implantation is far from a thermodynamical equilibrium process, one can ask about the role of the thermodynamic parameters on the final systems. Ion beam mixing experiments4-5 point out that the heat of formation plays an important role both on the final phases and mixing rates. In the case of Cu implanted in sintered A1N,6-7 the implanted ions were found to form small clusters with diameters of 6-16 A as a function of the implantation fluence and post-implantation annealing. The heat of formation for Cu-nitrides is positive while the ones for the intermetallic compound are slightly negative (Table I). Furthermore, the A1N system is very stable with a heat of formation of H.Hf° = —76.0 kcal/mol. What occurs in the case of an ion susceptible to form another nitride with a heat of formation close to the A1N one? With a 3136 http://journals.cambridge.org
J. Mater. Res., Vol. 10, No. 12, Dec 1995 Downloaded: 30 Mar 2015
A//y° = —80.8 kcal/mol for TiN formation, Ti seems to be a good candidate to answer this question. The goal of this article is to determine experimentally what are the chemical bonds resulting from Ti implantation in sintered A1N. A good understanding of the first steps of new phase formation during ion implantation in A1N could allow one to optimize the su
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